162 lines
5 KiB
D
162 lines
5 KiB
D
// Copyright Ferdinand Majerech 2014.
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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// Code that is currently unused but may be useful for future D:YAML releases
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module dyaml.unused;
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import std.utf;
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import tinyendian;
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// Decode an UTF-8/16/32 buffer to UTF-32 (for UTF-32 this does nothing).
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//
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// Params:
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//
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// input = The UTF-8/16/32 buffer to decode.
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// encoding = Encoding of input.
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//
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// Returns:
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//
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// A struct with the following members:
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//
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// $(D string errorMessage) In case of a decoding error, the error message is stored
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// here. If there was no error, errorMessage is NULL. Always
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// check this first before using the other members.
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// $(D dchar[] decoded) A GC-allocated buffer with decoded UTF-32 characters.
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auto decodeUTF(ubyte[] input, UTFEncoding encoding) @safe pure nothrow
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{
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// Documented in function ddoc.
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struct Result
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{
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string errorMessage;
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dchar[] decoded;
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}
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Result result;
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// Decode input_ if it's encoded as UTF-8 or UTF-16.
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//
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// Params:
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//
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// buffer = The input buffer to decode.
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// result = A Result struct to put decoded result and any error messages to.
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//
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// On error, result.errorMessage will be set.
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static void decode(C)(C[] input, ref Result result)
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{
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// End of part of input that contains complete characters that can be decoded.
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const size_t end = endOfLastUTFSequence(input);
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// If end is 0, there are no full chars.
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// This can happen at the end of file if there is an incomplete UTF sequence.
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if(end < input.length)
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{
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result.errorMessage = "Invalid UTF character at the end of input";
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return;
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}
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const srclength = input.length;
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try for(size_t srcpos = 0; srcpos < srclength;)
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{
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const c = input[srcpos];
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if(c < 0x80)
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{
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result.decoded ~= c;
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++srcpos;
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}
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else
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{
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result.decoded ~= std.utf.decode(input, srcpos);
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}
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}
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catch(UTFException e)
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{
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result.errorMessage = e.msg;
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return;
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}
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catch(Exception e)
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{
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assert(false, "Unexpected exception in decode(): " ~ e.msg);
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}
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}
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final switch(encoding)
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{
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case UTFEncoding.UTF_8: decode(cast(char[])input, result); break;
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case UTFEncoding.UTF_16:
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assert(input.length % 2 == 0, "UTF-16 buffer size must be even");
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decode(cast(wchar[])input, result);
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break;
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case UTFEncoding.UTF_32:
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assert(input.length % 4 == 0,
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"UTF-32 buffer size must be a multiple of 4");
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// No need to decode anything
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result.decoded = cast(dchar[])input;
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break;
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}
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if(result.errorMessage !is null) { return result; }
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return result;
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}
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// Determine the end of last UTF-8 or UTF-16 sequence in a raw buffer.
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size_t endOfLastUTFSequence(C)(const C[] buffer)
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{
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static if(is(C == char))
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{
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for(long end = buffer.length - 1; end >= 0; --end)
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{
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const stride = utf8Stride[buffer[cast(size_t)end]];
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if(stride != 0xFF)
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{
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// If stride goes beyond end of the buffer, return end.
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// Otherwise the last sequence ends at buffer.length, so we can
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// return that. (Unless there is an invalid code unit, which is
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// caught at decoding)
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return (stride > buffer.length - end) ? cast(size_t)end : buffer.length;
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}
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}
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return 0;
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}
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else static if(is(C == wchar))
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{
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// TODO this is O(N), which is slow. Find out if we can somehow go
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// from the end backwards with UTF-16.
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size_t end = 0;
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while(end < buffer.length)
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{
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const s = stride(buffer, end);
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if(s + end > buffer.length) { break; }
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end += s;
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}
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return end;
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}
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}
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// UTF-8 codepoint strides (0xFF are codepoints that can't start a sequence).
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immutable ubyte[256] utf8Stride =
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[
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1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
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1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
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1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
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1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
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1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
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1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
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1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
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1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
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0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
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0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
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0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
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0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
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2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
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2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
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3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
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4,4,4,4,4,4,4,4,5,5,5,5,6,6,0xFF,0xFF,
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];
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